Process for making soil and stain resistant carpet fiber

ABSTRACT

A method for producing carpet yarn produces yarn having substantial soil hiding, soil repelling and resistance to staining with acid dye characteristics. The yarn is made by forming at least one hollow trilobal fiber from a molten nylon polymer having an amine end group level below about 25 meq/kg, the fiber having a modification ratio of about 2 and a void volume of at least 3%; quenching the formed fiber sufficiently to solidify the molten nylon; immediately after quenching, at a yarn speed of at least 300 mpm, finishing the fiber with spin finish containing fluorochemical; fully drawing the finished fiber; texturing the finished yarn by a hot fluid texturing process; and subsequently, applying to the textured yarn a sulfonated stainblocker, the stainblocker being heated to at least 50° C. and applied while the fiber temperature is at least about 100° C. in the stainblocker application step. The yarn travels at a rate sufficient to permit fixation of the stainblocker while minimizing penetration of stainblocker into the yarn.

This is a divisional of application Ser. No. 08/171,369 filed Dec. 20,1993, now abandoned, which in turn was a continuation of Ser. No.07/914,680 filed Jul. 15, 1992, and now abandoned.

FIELD OF THE INVENTION

The present invention relates generally to carpet fibers and, moreparticularly, to carpet fibers having substantial soil hiding, soilrepellent and acid dye stain resistant characteristics and a process forproducing such fiber.

BACKGROUND OF THE INVENTION

As used herein, the term "modification ratio" ("MR") describes the ratioof the radius of the circle circumscribing the lobes of a lobal fiber tothe radius of the circle inscribed by the core of that fiber. The term"fiber" encompasses both staple fibers and continuous filaments. "Yarn"means a continuous strand of fiber in a form suitable for knitting,weaving, or otherwise intertwining to form a fabric.

Synthetic fibers used to make carpet yarn and ultimately carpet mustpossess certain characteristics in order for the carpet made from thesefibers to be durable and satisfactory floor covering. Due to high volumefoot traffic, carpets tend to become dull, dirty and reveal paths wherepeople habitually tread, e.g., the center of a hallway. As aconsequence, carpets should resist soiling for long periods and hide anysoil which does accumulate. As a further attribute, a carpet should beresistant to staining by materials commonly found in households andcommercial environments. One notorious source of staining is the aciddyes found in beverages like fruit juice and colored children's drinks.Various efforts have been directed to producing carpet fibers whichpossess as many of these attributes as possible.

Hollow trilobal fibers are known to generally provide soil hidingcharacteristics when used to make carpet. For example, U.S. Pat. No.5,208,107 which issued May 4, 1993 describes a hollow trilobal fiber.

Providing nylon polymers with reduced amine end group levels is known.For example, U.S. Pat. No. 4,097,546 to Lofquist describes the use ofmonocarboxylic acid or dicarboxylic acid as a molecular weight regulatorwhich also decreases the concentration of amine ends, preferably to 15to 25 meq/gm. Reducing amine end group levels contributes to acid dyeresistance by blocking the amine receptors for acid dyes.

Application of fluorochemicals to yarn is known to resist soil and repeloil. For example, U.S. Pat. No. 4,192,754 to Marshal et al. describes aspin finish containing a fluorochemical compound.

Stainblockers for imparting acid stain resistance to polyamide carpetingyarns are known as well. While present stainblocker technologyencompasses several chemical classes, of most concern here are certainaromatic-formaldehyde condensation products, some of which are alsoknown as novolacs, and other sulfonated materials. U.S. Pat. No.5,061,763 to Moss III et al. describes a stainblocker composition whichis prepared by polymerizing an acrylic monomer in the presence ofsulfonated aromatic-formaldehyde condensation products. Patentsdescribing the use of novolacs as stainblockers for carpets are U.S.Pat. No. 4,822,373 to Olson et al., which describes a polyamide treatedsubstrate having applied thereto a mixture of partially sulfonatednovolac resin and a polymethacrylic acid or copolymer thereof. U.S. Pat.No. 4,780,099 to Gresschler et al. describes polyamide fibers which aremade stain resistant by treating them with a sulfonated naphthyl orsulfonated phenol formaldehyde condensation product at a pH of between1.5 and 2.5.

Various ingredients including sulfonated phenolic resins, sulfonatedaromatic compounds, compounds of sulfonated phenolics and aldehydes,modified wax emulsions, fluorochemicals, acrylics and organic acids oflow molecular weight have been variously combined to provide stainresistance upon application to polyamide carpet. For example, U.S. Pat.No. 5,073,442 to Knowlton et al. describes such a composition.

Yet, most efforts to combine various known agents onto the fiber itselfhave been unsuccessful to some degree. Most efforts to combine variousknown agents to carpet yarn for soil repellency and stain resistancehave been only partially successful and then only at relatively slowspeeds (less than 100 mpm). Some of the difficulties encountered includeincompatibility of fluorochemical finish and stainblocker, tackiness ofthe stainblocker and migration of stainblocker to the fiber center.Surprisingly, the present invention allows a particularly effectivetreatment to carpet fibers through control of application conditions athigh speeds. The fiber produced by this process has excellent propertiesthat were previously unachievable in a fiber. These properties includeimproved soiling and staining resistance, soil resistance, superiorcover, superior appearance retention, low flammability, a firm hand andease of processing.

SUMMARY OF THE INVENTION

The present invention provides a method for producing carpet yarn havingsubstantial soil hiding, soil repellent and resistance to staining withacid dyes by forming at least one hollow trilobal fiber from a moltennylon polymer having an amine end group level below about 25 meq/kg, thefiber having a modification ratio of at least 2 and a void volume of atleast 3%; quenching the formed fiber sufficiently to solidify the moltennylon; immediately after quenching, at a yarn speed of at least 300 mpm,finishing the fiber with spin finish containing fluorochemical; fullydrawing the finished fiber; texturing the finished yarn by a hot fluidtexturing process; and subsequently, applying to the textured yarn asulfonated stainblocker, the stainblocker being heated to at least 50°C. and applied while the fiber temperature is at least about 100° C.During the applying, the yarn travels at a rate sufficient to permitfixation of the stainblocker while minimizing penetration ofstainblocker into the yarn.

Also provided is a carpet yarn which resists staining by acid dyes andhas substantial soil hiding and soil repellent characteristics. The yarnincludes 10 to 35 denier per filament hollow fibers defining a trilobalsurface with a modification ratio of at least 2 and a void volume of atleast 3 and formed from a nylon polymer having an amine end group levelbelow about 25 meq/kg. Fluorochemical is applied to the surface of saidfiber as a spin finish and stainblocker is applied to the spin finishedsurface immediately after texturing.

It is an object of this invention to prepare polyamide carpet yarn whichresists staining by acid dyes.

Another object of this invention to prepare polyamide carpet fiber whichresists and hides soil.

A further object of this invention is to apply stainblockers to carpetfiber such that the stainblockers resist penetrating into the fiber'sinterior and yet are fixed primarily on the surface of the fiber.

After reading the following description, related objects and advantagesof the present invention will be apparent to those ordinarily skilled inthe art to which the invention pertains.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a thread flow diagram of the process of the present invention.

FIG. 2 is a thread flow diagram of an alternate embodiment of theprocess of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To promote an understanding of the principles of the present invention,descriptions of specific embodiments of the invention follow andspecific language describes the same. It will nevertheless be understoodthat no limitation of the scope of the invention is thereby intended,and that such alterations and further modifications, and such furtherapplications of the principles of the invention as discussed arecontemplated as would normally occur to one ordinarily skilled in theart to which the invention pertains.

A first embodiment of the present invention involves a method forproducing carpet yarn which has resistance to staining by acid dyes andsoiling. The method involves forming and quenching a fiber from a nylonpolymer. The quenched fiber is finished with a spin finish containingfluorochemical; and subsequently, a stainblocker is applied at 50°-95°C. immediately after the texturizing operation while the fiber is noless than 100° C.

The first step involves forming the fiber. Fibers preferred in theinvention are hollow trilobal fibers having regular or irregularcross-sections, e.g., lobe spacing may be even or uneven. Suitablemodification ratios include 2 and higher. The void volume is at least 3%of the fiber cross-section, preferably 3-8% and most preferably, around5%. The fiber denier per filament ("dpf") should be suitable for therequirements of carpet yarn, that is, from 10-35 dpf, preferably from15-30, and most preferably, from 20-25 dpf. Continuous filament yarnsare preferred.

Useful nylon polymers include any fiber forming polyamide, especiallynylon 6 and nylon 6,6. Conventional melt spinning techniques may be usedaccording to the polymer being extruded. Spinning conditions should varyaccording to the cross-section to be made, i.e., the denier,modification ratio and void volume. A spinneret suitable for producingthe hollow trilobal should be used. One source of spinnerets is theKasen Nozzle Company.

The nylon polymer may be modified with an amine end group blocker toproduce an amine end group level below about 25 meq/kg of polymer. Amineend groups ("AEG") may be measured by dissolving nylon chip or dry yarnin a mixture of phenol and methanol solution at 50° C. and titrating thesolution with hydrochloric acid. The results are reported asmilliequivalent of AEG per kilogram of sample. Two suitable amine endgroup blockers are caprolactone and butrolactone. In most cases, about0.4% by weight of caprolactone or 0.6% by weight of butrolactone willproduce the desired AEG levels. Those of ordinary skill in the art,however, will recognize that extrusion temperature, reaction time andpressure affect AEG levels. The amine end group blocker is preferablyadded as a liquid at the throat of the extruder. Alternatively, the endgroup blocker may be added during the production of chip or duringpolymerization of the nylon 6. Other methods of incorporating the amineend group blocker may also be suitable.

Pigments and other colorants and, optionally, delusterants, flameretardants and other additives may be added to the polymer according tothe standard techniques for adding materials of the type. Pigments areavailable from various sources. Pigments exhibiting flame retardingaction such as carbon black and others disclosed in U.S. Pat. No.5,024,869 to Yeh et al. are especially preferred. When pigments areused, they may be added as a pigment concentrate which is blended withthe chip or added as a melt into a side-arm extruder. Again, all knownmethods for pigmenting (or adding colorant to) fiber may be used.

After extrusion, the still molten strands are quenched according toknown methods of quenching extruded fibers. For example, cooled air(14°-17° C.) flowed at 90 to 110 ft/min is crossed-flowed to the freshlyextruded molten filaments. Those ordinarily skilled in the art willreadily grasp that the quenching conditions can and should be varied toachieve target fiber denier, modification ratio and void volume.

Following quenching, the fiber is finished with a spin finish containinga fluorochemical. Advantageously, and according to the presentinvention, the fluorochemical finish is applied while the filaments arestill fresh from spinning and before other finishes, etc., are appliedto the filament surfaces. According to the invention, the finish issupplied to yarn traveling at about 300-1300 mpm. It is believed thatyoung yarn (freshly spun) enables the fluorochemical application speedspossible with the present invention. Preferably the fluorochemical isapplied at a rate sufficient to yield 350-750 ppm fluorine owl, and mostpreferably, 500 ppm. One suitable applicator for applying thefluorochemical containing spin finish is described in U.S. Pat. No.4,325,322, incorporated herein by reference.

There are a variety of fluorochemicals available for this purpose.Fluorochemical finishes featuring low flammability are especiallypreferred. They include those available from Minnesota Mining andManufacturing Company ("3M"), St. Paul, Minn. Preferred fluorochemicalsinclude FX360 from 3M.

Alternatively, the yarn may be wound up after finishing but beforedrawing. (See FIG. 2.) Conventional wind-up techniques may be used.

The finished fiber, whether wound up or supplied directly from finishingshould be drawn so that it is fully oriented. Typically, draw ratios of2.7-3.5 are used. Most normally a draw ratio of 3.0 is used.

After drawing, the yarn is texturized. Hot fluid jet texturizing methodsare used because they open the yarn structure. The jet texturizingmethod described in U.S. Pat. No. 4,522,774 is suitable, and this patentis incorporated herein by reference for the texturizing process taughttherein.

Following texturizing, a sulfonated stainblocker is applied to thefiber. Suitable stainblockers include those available from 3M as FX661and FX369 and from BASF Corporation, Parsippany, N.J., as BASF StainProtector. The stainblocker must be applied while the fiber is hot fromtexturing. Preferably, the fiber is at least about 100° C. Thestainblocker should be heated to about 50° C. or higher preferably atleast 70° C. Application rates of at least about 4% owf are preferred.The stainblocker may be applied by several methods including sprayingwith a spray nozzle or atomizer. During this step the yarn is travelingat 1200-3500 mpm.

While not wishing to be bound by theory, it is believed that freshlytexturized yarn has a more open structure. The open structurecontributes to a quick reaction of the fiber with the stainblocker. Butif the fiber was allowed to remain warm, the stainblocker wouldpenetrate too far into the interior of the fiber. To effectively blockstaining, stainblockers should be present at or near the fiber surface.Therefore, while warm conditions improve reaction of the fiber with thestainblocker, they also encourage penetration of the stainblocker intothe fiber. The fiber should be cooled rather immediately afterapplication of stainblocker. The high yarn speeds contribute to quickcool down. Evaporation of the aqueous solvent is another factor in rapidcool down. The goal is to fix the stainblocker to the fiber with limitedpenetration. Limitations on the yarn speed are set at the lower end bythe texturizing process and at the upper end by technology. The yarnmust travel sufficiently fast for the texturizing process to operate,typically at the very least 500 mpm.

Turning now to the figures for further understanding, FIG. 1 is a threadflow diagram showing the present invention as a one-step process. FIG. 1illustrates a thread flow diagram for a one-step process according tothe present invention. Nylon chips are fed into chip hopper for supplyto extruder 12. At extruder 12 (or chip hopper 10) various functionaladditives, e.g., pigments, AEG blockers, etc. may be added as discussedabove. Extruder 12 melts the nylon and forces it to spin beam 14 wherenylon filament 16 of the desired shape and denier are extruded andquenched. The spin finish containing fluorochemical is applied viaapplicator 18 and the yarn is passed to drawing stage 20 shown beingaccomplished by godet pairs 21 and 22 which operate at different speeds.

Following drawing, the yarn is textured by hot air bulking jet :25.Immediately following texturizing, stainblocker is applied by a suitableapplicator 27. The yarn might then be interlaced and wound-up.

FIG. 2 is a thread flow diagram of a two-step process of the presentinvention following wind-up after finish application. Yarn is extrudedand finish applied as shown through applicator 18 (FIG. 1) after whichit is wound-up as undrawn feed yarn 30 for later use. Undrawn feed yarn30 is unwound and drawn between godet pairs 32, 33 operating atdifferent speeds to facilitate drawing. After drawing, the yarn istexturized with hot air jet 35 and, while still warm from texturizing,stainblocker is applied with applicator 37. Air interlacing 39 andwinding 40 may follow.

Another embodiment of the present invention is carpet yarn. The yarn maybe prepared by the preceding process. Such a yarn provides good coveringpower and colorfastness with a firm hand. It exhibits desirable luster,has improved soiling and staining properties and has greater than 0.45watts/cm² radiant panel flammability when flame retardants are added.

A further embodiment of the present invention is a method for applyingstain-blockers to carpet yarn.

The invention will be described by reference to the following detailedexamples. The Examples are set forth by way of illustration, and are notintended to limit the scope of the invention. In the Examples, all partsare part by weight unless otherwise specified. In the Examples, thefollowing procedures were followed to produce the data:

Cut Pile Carpets

Cut pile carpets are made by standard tufting methods from cabled andheatset yarns. Carpet construction is 35 oz./yd, 1/8 gauge and 5/8" pileheight.

Level Loop Carpets

Loop pile carpets are made by standard tufting methods from non-heatsetyarns. Carpet construction is 28 oz/yd, 1/8 gauge and 3/8 " pile height.

Soiling Test

3×6 ft dyed carpet samples are installed in a heavily traveled corridorfor 100,000 passes. The samples are then cleaned with a standard vacuumcleaner or a steam extractor. A visual comparison is made for degree ofsoiling.

EXAMPLE 1

A trilobal hollow cross-section fiber, 2.7 MR and 5.0% void, is formedfrom nylon 6 (B700, relative viscosity of 2.7) having an amine end grouplevel of about 20 meq/kg is made by adding 2% (based on polymer weight)butyrolactone in the extruder. The following spinning conditions areused:

    ______________________________________                                        1.        Extruder temperature                                                          Zone 1            265° C.                                              Zone 2            270° C.                                              Zone 3            275° C.                                              Zone 4            280° C.                                              Zone 5            280° C.                                    2.        Extruder Pressure 1800 PSI                                          3.        Polymer Through   280 g/min                                         4.        Capillary Shape   trilobal                                          5.        Capillary/Spinnerette                                                                           68                                                6.        Denier            1300                                              ______________________________________                                    

A fluorochemical is applied to the yarn during spinning and astainblocker is applied during texturing. The fluorochemical spin finishis a mixture of fluorochemical (FX360 from 3M), lubricant, antistaticagent and emulsifier applied at a yarn speed of 800 mpm. Thestainblocker is FX369 from 3M. The stainblocker is diluted by 50% withwater, heated to about 70° C. and sprayed at 1.0 gallon per hour on asemiplug coming out of a texturing operation at about 150° C. and 1750mpm. The amount of fluorochemical and stainblocker applied to the yarnis about 500 ppm fluorine and four percent stainblocker. Level loop andcut pile carpets are made as described. Floor wear and soil, tetrapodwear, and various stain tests are performed on these samples. Theresults are presented in TABLE 1.

EXAMPLE 2 [Comparative Example]

A comparative yarn example is made having a trilobal cross-section(MR=2.6) with no void and with an amine end group of 35 meq/kg. Normalspin finish without the fluorochemical is applied at 1.5% FOY. Colddemineralized water is sprayed to the hot yarn during the texturingoperation. Level loop and cut pile carpets are made as described. Theresults of wear, soil and various stain tests are provided in Table 1.

                  TABLE 1                                                         ______________________________________                                                 Red Food Color                                                                           Coffee                                                             AATCC 175-1991                                                                           Grey Scale Soiling                                        ______________________________________                                        Level loop carpet                                                             Example 1  9            4                                                     Example 2  2            3                                                     Heatset cut pile                                                              Example 1                          Moderate                                   Example 2                          Severe                                     ______________________________________                                    

Although certain preferred embodiments of the invention have been hereindescribed for illustrative purposes, it will be appreciated that variousmodifications and innovations of the procedures recited may be effectedwithout departure from the basic principles which underlie theinvention. Changes of this type are therefore deemed to lie within thespirit and scope of the invention.

What is claimed is:
 1. A method for producing carpet yarn which hassubstantial soil hiding, soil repellent and resistance to staining withacid dyes comprising:(a) forming at least one hollow trilobal fiber froma molten nylon polymer having an amine end group level below about 25meq/kg, the fiber having a modification ratio of at least 2 and a voidvolume of at least 3%; (b) quenching the formed fiber sufficiently tosolidify the molten nylon; (c) immediately after quenching, at a yarnspeed of at least 300 mpm, finishing the fiber with spin finishcontaining fluorochemical; (d) fully drawing the finished fiber; (e)texturing the finished yarn by a hot fluid texturing process; and (f)subsequently, applying to the textured yarn a sulfonated stainblocker,the stainblocker being heated to at least 50° C. and applied while thefiber temperature is at least about 100° C., during said applying theyarn traveling at a rate sufficient to permit fixation of thestainblocker while minimizing penetration of stain- blocker into theyarn.
 2. The method of claim 1 and further comprising(g) winding up thefinished yarn prior to drawing.
 3. The method of claim 1 wherein saidforming is of a fiber having a void volume of approximately 5%.
 4. Themethod of claim 1 wherein said quenching is carried out with gas chilledto about 14°-17° C. supplied at about 90 to 110 ft/min.
 5. The method ofclaim 1 wherein said finishing is with a fluorochemical applied to yield350 to 750 ppm fluorine owf.
 6. The method of claim 5 wherein saidfinishing is with a fluorochemical applied to yield about 500 ppmfluorine owf.
 7. The method of claim 1 wherein said finishing is with afluorochemical metered to a slotted applicator.
 8. The method of claim 1wherein said drawing is at a draw ratio of about 2.7-3.5
 9. The methodof claim 1 wherein said applying is carried out at 500 mpm or faster.10. The method of claim 9 wherein said applying is carried out at1000-3500 mpm.